What is varicella?Varicella or chickenpox is a highly contagious disease with peak age at 5-9 years leading to rash. It is a self-limiting disease and occasionally leads to fever, pneumonia, liver damage and brain infection. Chicken pox can be very severe in immunocompromised patients e.g. in patients with cancer and can even lead to death.

If it occurs during pregnancy, there are 25% chances of transmission of the virus to fetus. If it occurs in first half of pregnancy it will lead to fetal varicella syndrome characterized by scarred skin, limb defects and eye defects. If it occurs in 2nd half of pregnancy, the child has chances of developing herpes zoster at an early age.

If it occurs within 21 days of delivery, there are 25% chances of newborn developing chicken pox.

Which high- risk group should receive Varicella vaccine and why?Varicella vaccine is definitely indicated in certain high-risk groups:
Immuno-compromised host: Varicella can be very severe in immunocompromised host as seen before. Hence such children should be immunized irrespective of age. One needs to give 2 doses of injections. Care should be taken to stop chemotherapy/steroids for at least 2 weeks before and after vaccination or at least for the first dose of vaccination.
Healthy adults and adolescents (>13 yrs. old): Those with no definite history of chicken pox in the past can be assumed to be susceptible, as subclinical cases of varicella are rare. Such patients have high morbidity and occasional mortality if they develop chicken pox. Ideally all such adults should be vaccinated but specially the following high risk groups:

i) Non-pregnant women of childbearing age.
ii) Adults in contact with children who are at high risk of complications of chicken pox e.g. family members of a child with leukemia.
iii) Those at high risk of exposure to chickenpox like teachers of young children, college students, day-care nursery workers, military personnel etc.
iv) Health personnel.

What about normal children? Who should be given the varicella vaccine?Universal vaccination of all children at 15-18 months of age and aubsequently at 5 years of age has been advocated in some countries including USA and India of late.

A normal child who develops chickenpox suffers for 1-2 weeks of disease. The complications are rare and mortality even more rare. But there are occasional cases of complications like encephalitis, pneumonia and even death in normal children. More important, it leads to social problems like the child missing school or even final exams as it usually occurs in months of Jan- March every year. Even the parents will have to take leave and lose wages for 7-14 days.

What is the schedule?It is to be given subcutaneous over left arm or thigh. It is given at 12-15 months of age and a second dose is given at 5 years of age. In older children and adults, 2 doses are given at 6-8 weeks interval.

What are the side effects?It is a very safe vaccine. Local side effects seen include pain, redness, swelling in <5% of vaccines. Systemic side effects like fever are rare. 3-7% of vaccines can develop varicella like rash, which are very mild with rapid recovery. It can occur within 6 weeks of vaccination.

What are the contraindications to Varicella vaccine?Firstly it is not indicated in those who have definite history of chickenpox in the past. It is contraindicated in-patients with neomycin hypersensitivity as the vaccine contains traces of neomycin. It is contraindicated in patients with immunodeficiency including symptomatic HIV and in children with acute leukemia on chemotherapy.

For patients with leukemia in remission, chemotherapy should be withheld for at least 2 weeks before and after the first dose of vaccine. Similarly patients on high dose of long-term steroids should be given the vaccine when steroids are temporarily withheld for at least 2 weeks before and after vaccine.

It is contraindicated during pregnancy and in fact pregnancy should be avoided for at least 6-8 weeks after vaccination.

What is herpes zoster?
Varicella and herpes zoster are manifestations of the same virus i.e. varicella virus. When a person comes in contact with the virus for the first time, he develops chickenpox. Even when he recovers, the virus remains latent in the nerves for years. In 15-20% of them, the virus is able to spread albeit locally along the nerve root causing herpes zoster. This occurs due to natural fading of immunity and hence occurs after the age of 40-50 years.

Herpes zoster, though usually a benign disease lasting for 7-10 days can lead to complications. Firstly, it can lead to pain, which can go on for months to years. Secondly, if it involves the face, it could also involve the eyes and unless one takes proper precaution, this can lead to permanent damage to vision. Lastly, herpes zoster if it occurs in immuno-compromised patients like HIV, it can lead to complications like pneumonia and brain damage.

Can herpes zoster be prevented?
Yes, by giving varicella vaccine before chickenpox develops. As seen, early herpes zoster occurs only after one contracts chickenpox virus and develops initially. When one takes chickenpox vaccine, one prevents contact with wild virus and hence prevents both chickenpox and herpes zoster.

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